The invention relates to a method and apparatus for reducing data throughput when transmitting data which characterize processes or objects, between computing elements communicating under time control, particularly in real time.
In computer units which communicate with one another in real time, the maximum bandwidths or transmission rates of the data transmission devices, including the protocol used for such communication, represent a bottleneck in the data interchange between the computer units. Usually, data quantities which exceed the maximum bandwidth are deleted or delayed during the transmission; and the sending computer has no information concerning the cutting-off or the delay of data quantities, including the portion of the data which has not been transmitted. As the result, the sending computer unit itself has no control over which data the receiving computer unit has received. It is therefore a disadvantage in the state of the art that it is essentially only possible either to tolerate this uncertainty or to accept additional management expenditures with respect to data transmission reliability in order to control the data transmitted to the receiving computer unit. According to the state of the art, these advantages are overcome by using relatively high-expenditure (and therefore high-cost) data transmission devices with a large transmission bandwidth.
It is therefore an object of the invention to provide a process and apparatus for transmitting data between computer units communicating under time control, which minimizes the data quantities to be exchanged between the computer units, while simultaneously preserving the information concerning the respective connected computer units, which is present in the interchanging computer units.
This and other objects and advantages are achieved by the communication method and apparatus according to the invention, in which, during each transmission interval, a sending communication computer decides whether to send updated (current) data to another communication computer in a different user area, using at least one extrapolation process which is running on both data-interchanging communication computers. In the sending communication computer, the current data, generated by external units assigned to the sending communication computer are compared with corresponding data extrapolated by the sending computer. Since the same extrapolated data are also generated in the same manner in the receiving communication computer for use in the external units assigned to it, the sending communication computer, taking into account the transmission path, has information concerning the data which are present in the receiving user area. On this basis, and as a result of the comparison of extrapolated data with current data, the sending communication computer decides whether to send current data to the receiving user area.
In order to design the extrapolation processes efficiently, the characteristics of objects or processes which are described by the data to be transmitted, are structured in corresponding formats such that, on the one hand, the objects or processes are described by as few data expenditures as possible and, on the other hand, the extrapolation processes achieve maximum efficiency in use of computing time. As a result, the data quantities to be transmitted per time unit are significantly reduced. Furthermore, the quality of the objects processed by the system or the number of described objects can be increased, while transmitting the same data quantities as in the state of the art.
The comparison (difference) values as between the current and extrapolated data sets are compared with threshold values for the decision concerning transmission. Together with a continuously updated list of priorities (by means of which a sequence, and thus a transmission point in time of the data to be transmitted is defined), these threshold values determine a maximal transmission error.
The system for transmission of data according to the invention particularly also has the advantage that, for communication between computer systems producing large quantities of data, it is possible to use data transmission devices with relatively low transmission bandwidths, which are reasonable in cost.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.